1. Field of the Invention
The present invention relates to an arteriostenosis inspecting apparatus which inspects presence or absence of arteriostenosis of a living person, and an ankle-blood-pressure measuring apparatus which measures a blood-pressure of an ankle of a living subject.
2. Related Art Statement
Atherosclerosis as a sort of arteriosclerosis is a disease that lipid, in particular, cholesterol deposits on walls of arteries and thereby thickens the arterial walls. Since atherosclerosis generates stenosis of an artery and thereby decreases its diameter, it is also called arteriostenosis or arteriosclerosis obliterans. There is known an inferior-and-superior-limb-blood-pressure-index measuring apparatus which can be used for inspecting arteriostenosis, by utilizing a fact that blood pressure lowers on a distal side of a body portion having arteriostenosis. The measuring apparatus is disclosed in, e.g., Japanese Patent No. 3,140,007 or its corresponding U.S. Pat. No. 6,355,000. The disclosed measuring apparatus includes a cuff worn on an inferior limb to measure a blood pressure of the inferior limb, and a cuff worn on a superior limb to measure a blood pressure of the superior limb, calculates an inferior-and-superior-limb blood-pressure index as a ratio of one of the inferior-limb blood pressure and the superior-limb blood pressure to the other, and inspects presence or absence of arteriosclerosis based on the thus calculated index.
For example, in the case where arteriosclerosis obliterans is inspected based on an inferior-and-superior-limb blood-pressure index, the index is calculated by dividing an inferior-limb systolic blood pressure by a superior-limb systolic blood pressure and, if the thus calculated index is greater than 0.9, it is judged that arteriostenosis is absent and, if the index is not greater than 0.9, it is judged that arteriostenosis is suspected.
In the above-indicated inferior-and-superior-limb-blood-pressure-index measuring apparatus, generally, an ankle is selected as the inferior limb and a cuff is worn on the ankle. Meanwhile, an ankle has two thick arteries, i.e., an anterior tibial artery and a posterior tibial artery. There are known some cases where one of the two arteries has stenosis but the other artery does not. As explained above, blood pressure lowers on a distal side of a stenotic portion. Since, however, an ankle has two thick arteries, if only one of the two arteries has stenosis and accordingly a blood pressure of the other artery free of stenosis does not lower, the blood pressure of the other artery is measured as a blood pressure of the ankle. Thus, even if one of the two arteries may have stenosis, a measured blood pressure of the ankle may be normal, and an inferior-and-superior-limb blood-pressure index calculated based on the measured ankle blood pressure may be normal. In this case, the inferior-and-superior-limb blood-pressure index cannot be used for finding arteriostenosis.
It is therefore an object of the present invention to provide an ankle-blood-pressure measuring apparatus which can measure an ankle blood pressure that can be used for calculating an inferior-and-superior-limb blood-pressure index that can be used for accurately inspecting presence or absence of arteriostenosis of an inferior limb of a living person, and an arteriostenosis inspecting apparatus which can accurately inspect presence or absence of arteriostenosis of an inferior limb of a living person.
The above object has been achieved according to a first aspect of the present invention. According to the first aspect, there is provided an ankle-blood-pressure measuring apparatus for measuring a blood pressure of an ankle of a living subject, comprising an inflatable cuff which is adapted to be worn on the ankle of the subject; a cuff-pressure changing device which decreases a pressure in the cuff from a pressure higher than a systolic blood pressure of the ankle; a distal-pulse-wave detecting device which is adapted to be worn on a distal portion of the subject that is located on a distal side of the ankle and detects a distal pulse wave produced from the distal portion; an increasing-point detecting means for detecting at least one increasing point where a magnitude of the distal pulse wave continuously detected by the distal-pulse-wave detecting device when the pressure of the cuff is decreased by the cuff-pressure changing device, significantly increases; and an ankle-blood-pressure determining device which determines a pressure of the cuff when the increasing-point detecting means detects the second increasing point, as a systolic blood pressure of one of a plurality of tibial arteries of the ankle of the subject that has stenosis.
According to this aspect, when the pressure of the cuff worn on the ankle is decreased, the distal-pulse-wave detecting device worn on the distal portion located on the distal side of the ankle continuously detects the distal pulse wave produced from the distal portion, and the increasing-point detecting means detects the increasing point where the magnitude of the distal pulse wave significantly increases. In the case where only one of anterior and posterior tibial arteries has stenosis, a pressure of the cuff when flow of blood resumes in the stenotic tibial artery is lower than a pressure of the cuff when flow of blood resumes in the non-stenotic tibial artery. Therefore, in the distal portion on the distal side of the cuff, amount of flow of blood significantly largely increases twice. Thus, in this case, the increasing-point detecting means detects two increasing points and accordingly the ankle-blood-pressure determining device determines the pressure of the cuff when the increasing-point detecting means detects the second increasing point, as the systolic blood pressure of the stenotic tibial artery.
The above object has been achieved according to a second aspect of the present invention. According to the second aspect, there is provided an arteriostenosis inspecting apparatus, comprising an ankle-blood-pressure measuring apparatus according to the first aspect; a superior-limb-blood-pressure measuring device which measures a systolic blood pressure of a superior limb of the subject; and an inferior-and-superior-limb-blood-pressure-index determining means for determining an inferior-and-superior-limb blood-pressure index of the subject, based on the systolic blood pressure of the ankle measured by the ankle-blood-pressure measuring apparatus and the systolic blood pressure of the superior limb measured by the superior-limb-blood-pressure measuring device.
If an inferior-and-superior-limb blood-pressure index is determined based on the systolic blood pressure of the stenotic tibial artery, measured by the ankle-blood-pressure measuring apparatus, and presence or absence of arteriostenosis is judged based on the thus determined index, the presence or absence of arteriostenosis can be accurately judged by a living person such as a medical person or the subject. According to this aspect, the inferior-and-superior-limb-blood-pressure-index determining means determines the inferior-and-superior-limb blood-pressure index based on the systolic blood pressure of the stenotic tibial artery, measured by the ankle-blood-pressure measuring apparatus. Therefore, if presence or absence of arteriostenosis is judged based on the thus determined index, it is possible to accurately judge the presence or absence of arteriostenosis.
The above object has been achieved according to a third aspect of the present invention. According to the third aspect, there is provided an arteriostenosis inspecting apparatus, comprising an inflatable cuff which is adapted to be worn on an ankle of a living subject; a cuff-pressure changing device which decreases a pressure in the cuff from a pressure higher than a systolic blood pressure of the ankle; a distal-pulse-wave detecting device which is adapted to be worn on a distal portion of the subject that is located on a distal side of the ankle and detects a distal pulse wave produced from the distal portion; an increasing-point detecting means for detecting at least one increasing point where a magnitude of the distal pulse wave continuously detected by the distal-pulse-wave detecting device when the pressure of the cuff is decreased by the cuff-pressure changing device, significantly increases; and an arteriostenosis judging means for judging that the subject has arteriostenosis, based on a fact that the increasing-point detecting means detects the second increasing point.
As explained above, if only one of the two tibial arteries has stenosis, the increasing-point detecting means detects two increasing points. Thus, based on a fact that the increasing-point detecting means detects the second increasing point, it is possible to judge that the subject has arteriostenosis. According to this aspect, when the pressure of the cuff worn on the ankle is decreased, the distal-pulse-wave detecting device worn on the distal portion located on the distal side of the ankle continuously detects the distal pulse wave produced from the distal portion, and the increasing-point detecting means detects the increasing point where the magnitude of the distal pulse wave significantly increases. In addition, the arteriostenosis judging means judges that the subject has arteriostenosis, based on the fact that the increasing-point detecting means detects the second increasing point. Thus, even in the case where one of the two tibial arteries does not have stenosis but the other tibial artery has stenosis, the present apparatus can judge that the subject has arteriostenosis. This improves the accuracy of judgment of presence or absence of arteriostenosis.
The above object has been achieved according to a fourth aspect of the present invention. According to the fourth aspect, there is provided an arteriostenosis inspecting apparatus, comprising an inflatable cuff which is adapted to be worn on an ankle of a living subject; a cuff-pressure changing device which decreases a pressure in the cuff from a pressure higher than a systolic blood pressure of the ankle; a distal-pulse-wave detecting device which is adapted to be worn on a distal portion of the subject that is located on a distal side of the ankle and detects a distal pulse wave produced from the distal portion; and a display device which displays the distal pulse wave continuously detected by the distal-pulse-wave detecting device when the pressure of the cuff is decreased by the cuff-pressure changing device.
According to the third aspect of the present invention, the arteriostenosis judging means automatically judges whether the subject has arteriostenosis. Meanwhile, if the distal pulse wave is displayed, a living person such as a doctor can judge, based on the thus displayed distal pulse wave, whether the subject has arteriostenosis. According to this aspect, when the pressure of the cuff worn on the ankle is decreased, the distal-pulse-wave detecting device worn on the distal portion located on the distal side of the ankle continuously detects the distal pulse wave produced from the distal portion, and the display device displays the thus detected distal pulse wave. If the distal pulse wave displayed by the display device has two increasing points at each of which the magnitude of the distal pulse wave significantly increases, it is possible to judge that one of the two tibial arteries does not have stenosis but the other tibial artery has stenosis.
The above object has been achieved according to a fifth aspect of the present invention. According to the fifth aspect, there is provided an arteriostenosis inspecting apparatus, comprising an inflatable cuff which is adapted to be worn on an ankle of a living subject; a cuff-pressure changing device which changes a pressure in the cuff; an ankle-pulse-wave detecting device which detects an ankle pulse wave produced from the ankle and transmitted to the cuff; a distal-pulse-wave detecting device which is adapted to be worn on a distal portion of the subject that is located on a distal side of the ankle and detects a distal pulse wave produced from the distal portion; an amplitude-difference-value determining means for determining an amplitude difference value indicating a degree of difference between respective amplitudes of respective heartbeat-synchronous pulses of the ankle pulse wave and the distal pulse wave that are detected by the ankle-pulse-wave detecting device and the distal-pulse-wave detecting device, respectively, in a state in which the pressure of the cuff is made lower than a systolic blood pressure of the ankle by the cuff-pressure changing device; and an arteriostenosis judging means for judging that the subject has arteriostenosis, based on a fact that the amplitude difference value determined by the amplitude-difference-value determining means is greater than a reference value.
In the case where a cuff is worn on an ankle and a distal-pulse-wave detecting device is worn on a distal body portion located on a distal side of the ankle, like each of the above-described aspects, it is possible to judge presence or absence of arteriostenosis of an inferior limb, in particular, arteriostenosis of a distal body portion located on a distal side of an ankle which arteriostenosis cannot be inspected by the above-described inferior-and-superior-limb-blood-pressure-index measuring apparatus. According to this aspect, the ankle pulse wave and the distal pulse wave are detected in the state in which the pressure of the cuff is made lower than the systolic blood pressure of the ankle by the cuff-pressure changing device, and the amplitude-difference-value determining means determines the amplitude difference value indicating the degree of difference between the respective amplitudes of the ankle pulse wave and the distal pulse wave. If the subject has arteriostenosis between the ankle where the cuff is worn and the distal portion where the distal-pulse-wave detecting device is worn, the amplitude of the distal pulse wave is attenuated by the stenosis and accordingly is detected as being smaller than the amplitude of the ankle pulse wave that is not influenced by the stenosis, so that the amplitude-difference-value determining means determines a large amplitude difference value. Thus, the arteriostenosis judging means can judge that the subject has arteriostenosis between the ankle where the cuff is worn and the distal portion where the distal-pulse-wave detecting device is worn, based on the fact that the amplitude difference value determined by the amplitude-difference-value determining means is greater than the reference value.
The above object has been achieved according to a sixth aspect of the present invention. According to the sixth aspect, there is provided an arteriostenosis inspecting apparatus, comprising an inflatable cuff which is adapted to be worn on an ankle of a living subject; a cuff-pressure changing device which changes a pressure in the cuff; an ankle-pulse-wave detecting device which detects an ankle pulse wave produced from the ankle and transmitted to the cuff a distal-pulse-wave detecting device which is adapted to be worn on a distal portion of the subject that is located on a distal side of the ankle and detects a distal pulse wave produced from the distal portion; a phase-difference determining means for determining a difference of respective phases of respective heartbeat-synchronous pulses of the ankle pulse wave and the distal pulse wave that are detected by the ankle-pulse-wave detecting device and the distal-pulse-wave detecting device, respectively, in a state in which the pressure of the cuff is made lower than a systolic blood pressure of the ankle by the cuff-pressure changing device; and an arteriostenosis judging means for judging that the subject has arteriostenosis, based on a fact that the phase difference determined by the phase-difference determining means is greater than a reference value.
Based on a phase difference in place of the amplitude difference employed according to the fifth aspect, it is possible to judge presence or absence of arteriostenosis of a distal body portion located on a distal side of an ankle. According to this aspect, the ankle pulse wave and the distal pulse wave are detected in the state in which the pressure of the cuff is made lower than the systolic blood pressure of the ankle by the cuff-pressure changing device, and the phase-difference determining means determines the difference of respective phases of the ankle pulse wave and the distal pulse wave. If the subject has arteriostenosis between the ankle where the cuff is worn and the distal portion where the distal-pulse-wave detecting device is worn, the phase of the distal pulse wave is delayed by the stenosis, so that the phase-difference determining means determines a large phase difference. Thus, the arteriostenosis judging means can judge that the subject has arteriostenosis between the ankle where the cuff is worn and the distal portion where the distal-pulse-wave detecting device is worn, based on the fact that the phase difference determined by the phase-difference determining means is greater than the reference value.